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whisky-actual / Community-JAS-39-C

GitHub for the JAS-39-C Gripen mod for DCS
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The mod introduces non-determinism into the DCS simulation - replays go out of sync #76

Open filiph opened 2 years ago

filiph commented 2 years ago

Hi there!

First of all, I love the mod! Congrats on making it and kudos on maintaining it!

As many others, I try to make videos from my DCS adventures, but unfortunately, whenever I use this particular mod, the replays are wildly different from the gameplay. For example, I win a dogfight flying the JAS 39 against, say, the Su-27. Then I hit replay and very soon, what goes on in the replay differs. The Gripen does what it should, but I can see the Su-27 make different maneuvers, which leads to the JAS 39 shooting into empty air, and so on.

I noticed that this does not happen with quite a few other mods. For example, the (admittedly way simpler) VSN JAS 39 mod doesn't have this problem. Using that mod, both the Su-27 and the JAS 39 behave (almost?) exactly the same in the replay as they did 'live'.

I also know that some other mods, even the commercial ones, have similar determinism problems.

I wonder if there's any understanding on why this could be. Is there, for example, a random function used anywhere in the mod's code? (If so, I can't find it.) Or is it a case of unpredictable performance and therefore running time of the simulation tic? Or something else entirely?

I've never worked on a DCS mod but I'm not completely unfamiliar with Lua, either. If you give me a few pointers or ideas, I'm more than happy to look into the problem.

whisky-actual commented 2 years ago

Hi,

It's hard to say without any more information. However, it's been a known fact that replays in DCS are broken at this moment. We could definitely investigate more in the future, but our current focus is development. Once we have a more stable version this kind of issue will be on the menu.

Thank you!